The invention relates to an electric forced-convection air heater suitable for permanent attachment to a wall or a ceiling, or as a free-standing room heater. It refers particularly to an electric air heater provided with an axial fan and an electric resistance heater mounted upstream of the fan impeller.
Most forced-air heaters of known design employ as heating elements coils of resistance wires suspended from ceramic supports which, in turn, are held in position by a metal structure. This kind of heating element is very labor intensive, since the coils have to be threaded through openings in the ceramic supports, a task which is necessarily carried out by manual labor.
Another kind of resistance heater consists of individual strips of a resistance alloy, threaded at their both ends into perforations of ceramic support members. The projecting ends of the strips are subsequently connected to an electric power source by soldering or clamping. It will be understood that this assembly is highly labor intensive and therefore, expensive.
Finally, my U.S. Pat. No. 4,090,061 discloses a resistance heater surrounding a centrifugal blower impeller and serving both as air heater and as outlet guide vanes. The heater is in form of a cage of parallel vanes which are at their alternate ends connected to the adjacent vanes by bridging pieces. The cage is positioned in circular recesses in opposite walls of the blower casing and held therein by friction and pressure. The manufacture of this heating element is labor-saving, but the position of the individual vanes in relation to each other and to the blower casing is not very exact and stable, frequently resulting in changes of the angle of incidence and of the spacing of adjacent vanes.